That Swirl is not a mascot it's a Debian logo. Mascot has to be a character that can represent the meaning.That's being said Debian is the only OS that can't make Os-tans mascot for it.Since Debian already have toy stories code name characters. Building something random mascots which conflict against or aren't match to code name it's freaking awkward.

I used to planned to draw something from stretch like takaju did but gotta cancelled to avoid code name mascot conflictions.

Taking that they've said into consideration, it would be something which represents the Debian Philosophy [Social Contract/DFSG].

So something that represents some of more of the following: freedom, flexibility, community, transparency, independence and stability. I'm sure there are plenty of animals that represent a couple of those or more.